Depends on the tune and how you drive it I would say. As long as you keep up on regular maintenance it should be good. I threw a turbo in mine around 180k and have been pushing 12 psi without issue. I think im around 206k right now.

 

Any amount of boost will reduce reliability in an engine that was designed to be N/A. No one can tell you how long it will last, but people run anywhere from 7-12 lbs on factory internals. A good tune and healthy engine is the key to longevity.

 

The k20a3 is generally safe up to around 300whp. How long it lasts will depend on how often you beat on it, how well you keep up on maintenance, and how healthy the engine is before you boost it. A girl in our group recently boosted her a3 with a log kit with a small turbo and is pushing around 260 on low boost (7-8psi on the supplied turbo). I believe it was a rev9 kit with a turbo that they advertise as around a 60 trim. The greddy kits run an even smaller turbo than that, which I believe is what mfarmakas is referencing. While you're out of boost it shouldn't be much less reliable than stock.

 

The elephant in the room is are you the first and sole owner of the engine from the jump... ??
-- if not, the previous owner could have dogged out the engine & did a poor job maintaining oil levels, how often they changed the oil, may have run a cheaper oil not made for performance driving, etc... I have seen people run kpro & bolt-ons, then part-it out and go back to stock completely fooling the next buyer with a clapped out engine.

My suggestion before boosting your engine, I would run a compression test, next set the engine to T.D.C.. Remove the valvecover and inspect the cam gears & timing chain to see how far off the timing is. If it is off in the slightest do step B below, after A

Since you do not have oil squirters, You need to make sure the oil pump is working correctly. The K20a3 crankshaft is not as good as the A/A2/Z1/Z3. The K20a3's connection rods are thinner and has a thinner rod bearing. Any kind of oiling issue will target the connection rod's at the bearing site connecting @ the crankshaft journals. Engines that are driven hard will weaken at the most important connection points. Honestly,

A: I would pull the cylinder head and install a new head gasket with ARP head-studs.

B: I would install a new oil pump, new oil chain, new oil chain tensioner, new timing chain tensioner, and new timing chain (replace the guides as well).

C: Service Valve Lash, new spark plug seals, new valvecover gasket, install all exhaust studs fort extra strength needed for turbo manifold & turbo weight (try to install a support brace for the ex. manifold)